Method, Apparatus, and System for Inferring Contaminated Air Exposure Level Based on Operation Information of Wearable Device or Portable Air Purifier

5. The method of claim 4, wherein the exposure level classifying engine is machine-learned by Classification or Regression analysis.

9. The apparatus of claim 7, wherein the at least one processor is configured to notify the user of information on at least one of the dust sensor, an air quality improvement effect by the portable air purifier, or the air contamination level.

11. The apparatus of claim 10, wherein the exposure level classifying engine is learned by Classification and Regression analysis with the learning data comprising the dust concentration data and the label data.